1. Field of the Invention
The invention relates to electronic devices and reduction of power consumption thereby and, more particularly, relates to a circuit and method for turning power on and off to conserve power consumed by a device, which circuit and method provide for quick ramp up of the device without significant loss of power conserved or loss of accuracy due to ramp up timing requirements.
2. Description of the Related Art
It is often desirable to provide electronics devices with power saving features. This is particularly the case, for example, in electronics devices powered by batteries. As is known, batteries are drained of power in operation over time. At some point after a period of operation, the batteries' useful life as a power source is exhausted. To increase the useful life of batteries powering electronic devices, then, it may be helpful to employ features in the devices that reduce power consumption and thereby allow for longer periods of operation without replacing or recharging batteries.
One particular problem with known power saving features in electronics devices is that those features often operate by turning off power to the devices when not in use or maintaining the devices in an idle state requiring reduced power. When the devices are not supplied with power or are supplied only with reduced power, the devices may require a quick power up (or "ramp up") which typically consumes large amounts of current and requires time which may not be available. Both response times and battery power required to ramp up the devices for use may be significant.
In particular, digital cordless telephones are an example of devices which must be ready to receive and convey communications on demand. When a battery is employed to power a remote unit of those telephones, the remote unit must typically be maintained with the base unit when not in use, where the battery for powering the remote unit is there recharged. When the remote unit is in use, however, it is not feasible to maintain the remote unit with the base unit because that would prevent the desired mobility of the remote unit away from the base unit. Of course, the cordless telephone is used for communications when the remote unit is located a distance away from the base unit. The remote unit when in use is, therefore, generally powered by batteries which are drained during communications use.
In such digital cordless telephones, telephonic communications signals are received by the base unit via the public telephone lines. The base unit and remote unit communicate the communications signals therebetween as RF signals. In operation, the remote unit receives RF signals transmitted by the base unit, which RF signals correspond to the signals received by the base unit from the public telephone lines connected to the base unit.
The remote unit, in receiving RF signals from the base unit, must be ready to receive those signals when and as transmitted by the base unit. This has required that the remote unit be fully ramped up when in use or that the remote unit have at least portions of the remote unit circuitry capable of receiving communicated RF signals fully ramped up for receipt of the signals.
As is clear, maintaining a device, or portions thereof, fully ramped up may be a significant drain of power, which is particularly significant if power is supplied by batteries, as may be the case with a remote unit of digital cordless telephones. Therefore, turning power off to a device, or portions thereof, at times when the device, or portions, is not being operated may conserve power. Though turning the power off may conserve power in some devices, the benefits of that power conservation may be lost if significant power is required to ramp up the device when operation becomes necessary. Also, many devices, such as the remote unit of digital cordless telephones, may require quick ramp up to accomplish desired functions when time dependency is important. An example of such desired functions when time dependency is important in remote units of digital cordless telephones is receipt by the remote unit of RF signals communicated from the base unit.
When it is necessary to quickly ramp up all or portions of an electronics device, such as RF signal reception features of the remote unit of a digital cordless telephone as described, a significant electrical current is typically required and, even with such current, it becomes difficult to design for desired ramp up timing. The requirement of significant current to ramp up a device is particularly a problem in battery powered devices. This is because obtaining a significant amount of current from a battery power source consumes a large portion of the power available from the battery. Designing for desired ramp up timing is also a significant concern because designs achieving quick ramp up in such circumstances tend to be operationally and functionally complex, if even possible to adequately attain. Thus, it may not be quite so beneficial to attempt to conserve battery power by turning off all or portions of the device to reduce battery consumption if turning on the device requires quick ramp up and significantly drains the battery.
The present invention provides power conservation advantages that may otherwise be lost. As will be appreciated by those skilled in the art, the present invention can provide advantages in many instances in which quick ramp up, with power conservation, is desired. As is clear, the invention is an improvement in the art and technology. Though the background of the invention has been described, in part, with respect to cordless telephone application, the invention has other and varied application as will be hereinafter more fully understood.